Freezers are as dry as can be. You ever see 'freezer burn'? It will dry a steak to weird grey jerky if not sealed properly. The big issue with the freezer is guaranteed condensation once whatever is frozen gets removed. With beans this translates to ALWAYS let your vault reach room temp before actually opening, or at the very least the pack you removed. I remove packs right inside the freezer I avoid removing the vault if possible. Extra insurance I have rice in the vault to absorb any nasty condensation instantly. It works like this: Air tight at room temp, seeds stay viable for a Max of three years. Air tight in fridge, make it a safe five with half of them making ten years. Freezer can extend seed life 25 years and beyond. Cryogenic storage of seeds have been happening for a few decades, folks reckon we can germinate those a few thousand years from now. Remember, a seed is not alive. It is code. DNA is code for processes. Only thing really needed to activate the code and start the process of iteration is water. Once the process runs it can not be interrupted, interrupting life process equals death. But before the water hits the seed, it is pure code. DNA is a protein sequence. It can remain intact through a journey into space.